The present invention relates to heated make-up air systems, and more particularly to a heated make-up air system having controls for controlling the flow of air through the system.
Commercial kitchens typically include one or more exhaust fans that remove smoke, steam and other air polluting substances from areas around stoves, grills, ovens, dishwashers, etc. To replenish the exhausted air, commercial kitchens typically utilize what is termed make-up air systems that draw outside air into the kitchen. These make-up air systems basically comprise a duct structure open to both the outside air and the kitchen, a fan for blowing air through the duct structure into the kitchen, and a direct-fired gas burner for heating the air passing through the duct.
As is appreciated, in order to maintain optimum burner efficiency, it is important to provide the proper mixture of air and gas at the burner site. This essentially means that the flow of air through the duct and past the burner should be controlled. It is recognized that the differential pressure across the burner is an important parameter to consider when controlling the flow of air through the duct and when attempting to maintain optimum burner efficiency. More particularly, it is desirable to maintain the pressure differential across the burner generally constant during the operation of the burner. In controlling the pressure differential across the burner, heating systems in the past have achieved this by varying the flow rate of air passing the burner.
One such approach to controlling the flow of air past the burner has entailed the use of motorized dampers such as disclosed in U.S. Pat. No. 3,591,150. Typically, these dampers are located adjacent the burner, just downstream from the burner, and are designed to open and close and consequently vary the open area within the duct through which the air passes. This effectively varies the flow rate of air through the duct and past the burner and in the process tends to control the volume and velocity of air passing adjacent the burner and in the end does in fact control, to at least some degree, the pressure differential across the burner. However, systems such as motorized dampers are often slow to react to changes in air flow upstream from the burner or other air flow parameters that impact air flow and air velocity and consequently the pressure differential across the burner. Consequently, because of such slow reaction times, motorized dampers of the type disclosed in U.S. Pat. No. 3,591,150 do not always maintain the optimum air flow conditions around a direct-fired gas burner.
The present invention entails a make-up air system for heating outside air and directing the heated air into a kitchen or other areas to replace exhausted air. This system comprises a duct structure and a fan for moving air through the duct. A direct-fired burner is provided for heating the air moving through the duct. Disposed adjacent the burner is at least one spring biased moveable panel or profile plate for varying the air flow past the burner and through the duct.
In one embodiment of the present invention the spring-biased moveable panel functions to control the air flow through the duct and past the direct-fired burner. Specifically, the control is aimed at maintaining a generally constant differential pressure across the burner.
In one particular embodiment of the present invention, the direct-fired burner is mounted within a duct structure. Adjacent the burner there is provided an opening in the duct through which air passes. A pair of pivotally mounted and laterally spaced moveable panels are mounted in the opening, with each panel being moveable from a closed position to an open position. Each of the panels are spring-biased towards the closed position. Thus, as the flow rate of air increases through the duct, the pressure associated with the increased flow rate is effective to open the moveable panels and consequently vary the flow rate through the duct and past the burner.